The plots of Rt over time are showing a plateau in the estimated values, following a period of downwards trends from the introduction of the national Tier 4 restrictions and the beginning of the Christmas period. Many of the Rt values are below 1, notably in London, the EE and the SE, but remain higher than 1 in the SW, NW, NE and YH where the number of infections is increasing (SW, NW, NE) or plateauing (YH).
Incidence of deaths which had levelled off during the last week of November / first week of December, with some falls noted in the NE, NW, and YH, EM and WM started to climb significantly throughout December and early January in all regions. The deaths, which are now at a level similar to (e.g. London and WM) or higher than the first wave (SE and EE) are predicted to start falling in most regions, with the exception of regions where the number of new infections is still growing (SW, NW, NE).
In most regions, a downward trend in Rt started around the time of the launch of Tier 4 restrictions on Saturday 19th December appears to have been consolidated by the Christmas holiday period and the nationwide lockdown announced on the 5th January. It is difficult to separate the individual impacts of each, though in four regions (EE, London, SE and WM), the sharpest drop coincides with the timing of this latest lockdown, whereas in the Northern regions (NE, NW, YH) there is no appreciable decline in Rt after an initial drop when schools first closed over the Christmas period. In these regions Rt remains above 1.
However, due to the recency of the lockdown, its estimated impact is highly volatile and, with a high likelihood, could change over the coming week. This, combined with the conflicting signals from the two primary data streams (over a number of weeks the deaths continue to increase while prevalence declines), gives a reduced confidence in our outputs this week. Other indicators (e.g. hospital bed prevalence, case data etc) currently suggest a declining epidemic, so an estimate of positive epidemic growth may be a little unreliable. Conversely, it is this data conflict that leads to a very low estimate for Rt in EE, which should be treated with caution. Regardless of current trends, the prevalence of infection remains high and the demand on healthcare services is currently extreme, so continued restrictions are essential to lower these levels and to gain control over transmission over the coming period.
Real-time tracking of an epidemic, as data accumulate over time, is an essential component of a public health response to a new outbreak. A team of statistical modellers at the MRC Biostatistics Unit (BSU), University of Cambridge, are working to provide regular now-casts and forecasts of COVID-19 infections and deaths. This information feeds directly to the SAGE sub-group, Scientific Pandemic Influenza sub-group on Modelling (SPI-M), and to regional Public Health England (PHE) teams.
We fit a transmission model (Birrell et al. 2020) to a number of data sources (see ‘Data Sources’), to reconstruct the number of new COVID-19 infections over time in different age groups and NHS regions, estimate a measure of ongoing transmission and predict the number of new COVID-19 deaths.
We use:
Data are stratified into eight age groups: <1, 1-4, 5-14, 15-24, 25-44, 45-64, 65-74, 75+, and the NHS England regions (North East and Yorkshire, North West, Midlands, East of England, London, South East, South West).
Value of \(R_t\), the average number of secondary infections due to a typical infection today.
The percentage of a given group that has been infected.
NB: negative growth rates are rates of decline. Values are daily changes.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | 0.01 | -0.02 | 0.03 |
| East of England | -0.10 | -0.15 | -0.05 |
| East Midlands | -0.01 | -0.06 | 0.04 |
| London | -0.05 | -0.10 | 0.00 |
| North East | 0.02 | -0.04 | 0.07 |
| North West | 0.02 | -0.03 | 0.06 |
| South East | -0.04 | -0.09 | 0.01 |
| South West | 0.03 | -0.03 | 0.08 |
| West Midlands | -0.02 | -0.07 | 0.04 |
| Yorkshire and The Humber | 0.01 | -0.05 | 0.06 |
Halving times in days, if a region shows growth than value will be NA.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | NA | 42.57 | NA |
| East of England | 6.54 | 4.29 | 13.28 |
| East Midlands | 70.83 | 10.80 | NA |
| London | 13.70 | 6.67 | 328.02 |
| North East | NA | 19.22 | NA |
| North West | NA | 25.92 | NA |
| South East | 15.80 | 7.07 | NA |
| South West | NA | 22.41 | NA |
| West Midlands | 45.02 | 10.07 | NA |
| Yorkshire and The Humber | NA | 13.93 | NA |
Doubling times in days, if a region shows decline then the value will be NA.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | 107.88 | 21.50 | NA |
| East of England | NA | NA | NA |
| East Midlands | NA | 17.14 | NA |
| London | NA | NA | NA |
| North East | 41.28 | 10.60 | NA |
| North West | 30.32 | 10.81 | NA |
| South East | NA | 59.36 | NA |
| South West | 24.94 | 8.60 | NA |
| West Midlands | NA | 19.56 | NA |
| Yorkshire and The Humber | 114.39 | 11.17 | NA |
NB: negative growth rates are rates of decline. Values are daily changes.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | -0.02 | -0.03 | -0.01 |
| East of England | -0.05 | -0.06 | -0.04 |
| East Midlands | -0.02 | -0.04 | 0.01 |
| London | -0.04 | -0.05 | -0.02 |
| North East | 0.00 | -0.03 | 0.04 |
| North West | 0.01 | -0.02 | 0.04 |
| South East | -0.03 | -0.05 | -0.01 |
| South West | 0.01 | -0.02 | 0.05 |
| West Midlands | -0.02 | -0.04 | 0.01 |
| Yorkshire and The Humber | -0.01 | -0.04 | 0.02 |
Halving times in days, if a region shows growth than value will be NA.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | 39.29 | 26.70 | 96.24 |
| East of England | 12.56 | 11.02 | 16.00 |
| East Midlands | 41.41 | 18.90 | NA |
| London | 18.73 | 13.71 | 44.03 |
| North East | NA | 26.96 | NA |
| North West | NA | 36.23 | NA |
| South East | 19.86 | 14.14 | 63.06 |
| South West | NA | 34.13 | NA |
| West Midlands | 39.22 | 18.42 | NA |
| Yorkshire and The Humber | 56.41 | 19.42 | NA |
Doubling times in days, if a region shows decline then the value will be NA.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | NA | NA | NA |
| East of England | NA | NA | NA |
| East Midlands | NA | 51.29 | NA |
| London | NA | NA | NA |
| North East | 805.87 | 17.41 | NA |
| North West | 89.91 | 15.67 | NA |
| South East | NA | NA | NA |
| South West | 73.23 | 14.16 | NA |
| West Midlands | NA | 52.97 | NA |
| Yorkshire and The Humber | NA | 29.79 | NA |
The blue lines is show when interventions have been introduced (lockdown on 23 Mar and the relaxation of measures on 11 May), and the red line shows the date these results were produced (25 Jan).
The figure below shows the probability that \(R_t\) is greater than 1 (ie: the number of infections is growing) in each region over time. Clicking the regions in the legend allows lines to be added or removed from the figure.
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